[Ggfpc]

Hey! I bought this Tamron macro for film scanning and I'm seeing a weird issue with the aperture ring. Whenever I rotate one stop at the time.

The diaphragm only closes on some stops. I've included a video example.

This happens on camera and outside of the camera as well. I'm using a minolta adaptall mount.

Does anyone know what could be causing this?

https://v.redd.it/djb2v7cuxus91

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Last edited by Not a Number; 10-10-2022 at 08:34 AM.

[Not a Number]

Most likely oil on the blades. The lens could probably benefit from Cleaning Lubrication and Adjustment (CLA).

[marcusBMG]

OK you have the later 52BB adaptall 90mm. Sticky iris is a known issue with this lens. I have tried fixing this myself with partial success. Check out:

Adaptall diaphragm

It's not really clear to me what the problem is exactly. I don't notice oil or anything obvious on the iris blades. When done manually with a finger the mechanics seem ok. Tweaking the spring position seems to help. I have the impression that the mechanism is finely balanced and with age, a little bit of dirt/dust or something, this starts to happen.

[Ggfpc]

OK you have the later 52BB adaptall 90mm. Sticky iris is a known issue with this lens. I have tried fixing this myself with partial success. Check out:

Adaptall diaphragm

It's not really clear to me what the problem is exactly. I don't notice oil or anything obvious on the iris blades. When done manually with a finger the mechanics seem ok. Tweaking the spring position seems to help. I have the impression that the mechanism is finely balanced and with age, a little bit of dirt/dust or something, this starts to happen.

Is this something that a professional would know how to fix?

[marcusBMG]

Frankly, I don't know. Most camera repair shops don't work/are no longer familiar with old MF lenses. You might find a techie who is "old school" or willing to have a go. it's not difficult to go as far as I did. I suggest diy.

[kypfer]

It's just possible the Minolta mount is faulty and/or not fitted correctly.
I'd suggest removing the mount and operating the lens without a mount just to check the fault is still apparent.
With the mount removed, set the lens to it's smallest aperture and push the little wheel/roller to check the aperture mechanism.
Good luck

[Ggfpc]

OK you have the later 52BB adaptall 90mm. Sticky iris is a known issue with this lens. I have tried fixing this myself with partial success. Check out:

Adaptall diaphragm

It's not really clear to me what the problem is exactly. I don't notice oil or anything obvious on the iris blades. When done manually with a finger the mechanics seem ok. Tweaking the spring position seems to help. I have the impression that the mechanism is finely balanced and with age, a little bit of dirt/dust or something, this starts to happen.

So I tried this and had to release the tension on the spring by as much as I could by shortening the travel path. Now when I push the ring to f32 it snaps to the pin hole and I can adjust the aperture in reverse starting from f8 all the way to f2.5 . Can't complain, is better than what I had before, but now the aperture ring is continuous, it doesn't snap. Did this happen to yours as well?

[marcusBMG]

if you mean the aperture ring doesn't click, that is due to the ball bearing not the spring. Did you replace the ball bearing correctly (see pic #4 in my post in the linked thread on mflenses)?

[Ggfpc]

if you mean the aperture ring doesn't click, that is due to the ball bearing not the spring. Did you replace the ball bearing correctly (see pic #4 in my post in the linked thread on mflenses)?

Ah that makes sense, I tried to understand based on the pics but couldn't figure it out, I had to follow the article you posted. The ball bearing fell from the lens and I think it's lost forever.
Still, with it's limitations it's a great lens, and you were super helpful. Thanks!